Breaking the SLI "Code"

With the flood of nForce4 motherboards getting ready to enter the market, we had a decent selection of very recent nForce4 Ultra and nForce4 SLI motherboards. We also had both the SLI and the Ultra versions of the DFI based on the same PCB. With this wide selection of boards, we could look at the differences in the Ultra and SLI chipset and also confirm that they were not unique in any way.

If you look closely at the pictures of the SLI and Ultra, you will see that the chipset themselves appear identical. However, a closer look at the resistors and pads surrounding the chip shows some differences. The resistors appear the same on both, but there are 3 sets of resistor pads that are closed on the SLI chipset while just two sets are closed on Ultra. The vertical set of resistor pads just to the right edge of the chip itself is closed on SLI and open on Ultra. We could find no other obvious differences in the 2 chipsets. Could it be this simple?

We closed the set of resistor pads on the DFI LANParty UT nF4 Ultra-D with conductive paint, as you can see in the photo below.

We set the jumpers to SLI, attached the top bridge from an SLI board, since the Ultra boards do not ship with an SLI bridge, and fired up the system. The system was immediately recognized as an SLI chipset on boot and in Windows XP by our latest 71.40 Forceware drivers. Our little bit of very easy modification had "turned" the Ultra chipset into SLI. We no longer had driver limitations and performance was now exactly the same as the performance that we achieved with a normal SLI chipset.

We also tried modifying an Ultra to SLI with an ordinary #2 pencil. It worked perfectly, and with there being so much room around the set of resistor pads, you don't have to be that neat. If you close the pads, you have converted the Ultra to SLI. Those of you who remember Athlon XP modding for CPU speed will recall how close the sets of pads were in that mod. This required masking and careful painting of the pads to be closed. With the Ultra to SLI mod, there is huge real estate around the resistor on which you are working. As a result, even "all thumbs" modders should have an easy time with this one.

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85 Comments

what wrong with nvidia making a little money. i'd like to see a healthy ati and nvidia so they would make cards cheaper(older models) and better every six months. if we dont support these companies, then imagine a motherboard with no exspansion slots as companies start to intergrate everything. ati/nvidia are starting to branch out into other sectors, and id gladly support them for "cinematic" graphics. i have an an8-sli i bought for 199.99 from ZZF with a 6800gt and 6600gt so i can run 4 lcds. worth every penny...Reply

For those of you who are asking for an application for this mod, I have one. I want to play HL 2 now. I don't have enough money to afford an SLI rig, but I can scrape together enough for a 6600GT and this board. This would be significantly better than what I'm running right now. I want SLI as an upgrade path so when the 6600GT costs as much as the 9600 does now, I can buy another one and get a very affordable boost in proformance. And I'm relatvely sure that I will be able to find an SLI bridge within the next year so that takes care of that issue too.

Of course this doesn't make any sense for someone who is running Dual 6800 Ultras, this is a cost lowering solution, think about what people on a budget are actually buying and how this could help them.Reply

Thank you Wesley for the intriguing article & detective work. It's really neat to have a resource who's not afraid to be your guinea pig and risk frying a very precious commodity right now, an nF4 board :)

#30 - I don't see why A and B are exclusive -- why can't they keep producing and shipping Ultra chips in current architecture while at THE SAME TIME preparing a change to prevent this mod form working & then jus switch to that when it's ready?

#50 LOL, never spent more tha $200 on a single piece of compuer equipment?!?! I can tell that you weren't buying computers in the 80s!!Reply

The graphs have been updated with results from a single Gigabyte 6600 GT and the "dual 6600GT on a single card" Gigabyte 3D1 running in x16/x2 dual video mode. The Gigabyte 3D1 provides the interesting possibility of a form of SLI performance on single x16-slot Ultra boards with the SLI mod.
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I have never spent anything more than $200 for a single computer equipment. And i don't plan to in the future.

Hopefully, Via could get their act together faster and release an sli solution for guys like me on the cheap. Honestly, I bought an Asrock k7v88 at newegg for $50 and it overclocked my 2500+ barton to a 3200+ like a champ, and it was a via kt880 chipset, a very good performance competitor to the nforce2.

i mean i just bought an epox nforce 3 250gb at newegg for $70 for my sempron 3100+ clocked at 2.4ghz, and if an sli solution comes for around $100, i will surely hop on the pci-express boat, and maybe buy an athlon 64.Reply

ALL - I have some very interesting numbers with the Gigabyte 3D1 dual-GPU in single GPU vs. Dual GPU x16/x2 mode on the DFI. As I said earlier, the 3D1 does not work properly in x8/x8 mode in any SLI board except the Gigabyte, but it does work fine in x16/x8 mode on both the SLI and modded SLI DFI with SLI jumpers in normal (x16/x2) position instead of SLI (x8/x8) position. I am considering adding the numbers to the charts.Reply